Seismic and geodetic evidence for grounding-line control of Whillans Ice Stream stick-slip events

AbstractWe summarize new observations of the deceleration and stick–slip motion of Whillans Ice Stream (WIS), Antarctica. We refine the location of the large sticky spots that resist motion between slip events, the locations of which are controlled by the patterns of subglacial water flow. Our examination of the long-term velocity time series for the ice stream reveals that the decadal-scale deceleration is not occurring at a steady rate, but varies at the sub-decadal timescale. This unsteady deceleration modulates the temporal evolution of a broad (~50 km across) surface-elevation bulge forming at the junction between the relatively narrow upstream portion of the ice stream and broad ice plain that constitutes the downstream end of WIS. Comparison of observations from April 2003 and November 2010 reveals significant changes in the tidally modulated stick–slip cycle that regulates motion on the ice plain. We observe that the timing of slip events has become less regular in response to decreased flow speed in the upstream portions of the ice stream. The decreased regularity of slip events has reduced the release of stored elastic strain during slip events, increasing the rate of deceleration.

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Changes in the ice plain of Whillans Ice Stream, West Antarctica

Journal of Glaciology ◽

10.3189/172756505781829070 ◽

2005 ◽

Vol 51 (175) ◽

pp. 620-636 ◽

Cited By ~ 17

Author(s):

Robert Bindschadler ◽

Patricia Vornberger ◽

Laurence Gray

Keyword(s):

West Antarctica ◽

Ice Shelf ◽

Ross Ice Shelf ◽

Ice Stream ◽

Whillans Ice Stream ◽

Grounding Line ◽

Local Areas ◽

The Mean ◽

Geometric Changes ◽

Thinning Rate

AbstractData from the mouth of the decelerating Whillans Ice Stream (WIS), West Antarctica, spanning 42 years are reviewed. Deceleration has continued, with local areas of both thinning and thickening occurring. The mean thinning rate is 0.48 ± 0.77 ma–1. No consistent overall pattern is observed. Ice thickens immediately upstream of Crary Ice Rise where deceleration and divergence are strongest, suggesting expanded upstream influence of the ice rise. Thinning is prevalent on the Ross Ice Shelf. Grounding-line advance at a rate of 0.3 km a–1 is detected in a few locations. Basal stresses vary across an ice-stream transect with a zone of enhanced flow at the margin. Marginal shear is felt at the ice-stream center. Mass-balance values are less negative, but larger errors of earlier measurements mask any possible temporal pattern. Comparisons of the recent flow field with flow stripes suggest WIS contributes less ice to the deep subglacial channel carved by Mercer Ice Stream and now flows straighter. The general lack of geometric changes suggests that the regional velocity decrease is due to changing basal conditions.

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Dynamics of Stick-Slip Motion, Whillans Ice Stream, Antarctica

Quaternary International ◽

10.1016/j.quaint.2012.08.1876 ◽

2012 ◽

Vol 279-280 ◽

pp. 536

Author(s):

J. Paul Winberry

Keyword(s):

Stick Slip ◽

Ice Stream ◽

Whillans Ice Stream ◽

Stick Slip Motion ◽

Slip Motion

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Grounding-line dynamics and margin lakes

Annals of Glaciology ◽

10.3189/2014aog66a216 ◽

2014 ◽

Vol 55 (66) ◽

pp. 87-96 ◽

Cited By ~ 11

Author(s):

M.J. Fried ◽

C.L. Hulbe ◽

M.A. Fahnestock

Keyword(s):

Smooth Surfaces ◽

Line Position ◽

West Antarctica ◽

Main Trunk ◽

Ice Stream ◽

Whillans Ice Stream ◽

Grounding Line ◽

Different Ages ◽

History Of ◽

Regional History

AbstractAt both corners of the now stagnant Kamb Ice Stream (KIS, West Antarctica) outlet, shear margins of different ages confine wedge-shaped areas with relatively flat, smooth surfaces that stagnated before the main trunk of the ice stream. We identify these features as lakes or past lakes, and consider scenarios for their development in a regional history of ongoing adjustment to grounding-line position. We focus here on the centuries leading up to the recent stagnation of KIS, a time when its grounding line appears to have advanced >100km from an earlier upstream location. Starting from stagnation of Crary Ice Rise and changes in the grounding zone of Whillans Ice Stream, we trace feedbacks associated with local thickening, ice grounding and thickness transients that both advance the grounding line and leave remnant lakes in their wake. These lakes in turn promote the development of secondary margins that may appear as ‘margin jumps’ in the ice record.

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Stick–slip behavior of ice streams: modeling investigations

Annals of Glaciology ◽

10.3189/172756409789624274 ◽

2009 ◽

Vol 50 (52) ◽

pp. 87-94 ◽

Cited By ~ 42

Author(s):

Olga V. Sergienko ◽

Douglas R. MacAyeal ◽

Robert A. Bindschadler

Keyword(s):

West Antarctica ◽

Ice Streams ◽

Stick Slip ◽

Ice Stream ◽

Whillans Ice Stream ◽

Spatial Propagation ◽

The Difference ◽

Stick Slip Motion ◽

Transitional Phase ◽

Slip Motion

AbstractA puzzling phenomenon of ice-stream flow is the stick–slip motion displayed by Whillans Ice Stream (WIS), West Antarctica. In this study we test the hypothesis that the WIS stick–slip motion has features similar to those of other known stick–slip systems, and thus might be of the same origin. To do so, we adapt a simple mechanical model widely used in seismology to study classic stick–slip behavior observed in tectonic faults, in which the difference between static and dynamic friction allows for the generation and spatial propagation of abrupt slip events. We show how spatial variability in friction properties, as well as a periodic forcing intended to mimic the effect of tides, can reproduce the observed duration and periodicity of stick–slip motion in an ice stream. An intriguing aspect of the association of WIS with mechanical stick–slip oscillators is that the onset of stick–slip cycling from a condition of permanent slip appears to be associated with the reduction in overall speed of WIS. If this association is true, then stick–slip behavior of WIS is a transitional phase of behavior associated with the ice stream's recent deceleration.

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